Unit 6: Array

Question 1

How do you initialize an array?

Answer 1

type[] name = new type[int];
or
type[] name = {type, type, …};

Question 2

What is the defining characteristic of an array?

Answer 2

An array is of a fixed size.

Question 3

When would you use a for-each loop instead of a for loop?

Answer 3

When you want to access every element of an array and want to refer to elements through a variable name instead of an array index.

Question 4

How do you find the size of an Array?

Answer 4

Array.length

Question 5

Which of the following correctly initializes an array arr to contain four elements
each with value 0?
I int[] arr = {0, 0, 0, 0};
II int[] arr = new int[4];
III int[] arr = new int[4];
for (int i = 0; i < arr.length; i++)
arr[i] = 0;
(A) I only
(B) III only
(C) I and III only
(D) II and III only
(E) I, II, and III

Answer 5

(E) I, II, and III

Question 6

Refer to the following code segment. You may assume that arr is an array of int
values.
int sum = arr[0], i = 0;
while (i < arr.length)
{
i++;
sum += arr[i];
}
Which of the following will be the result of executing the segment?
(A) Sum of arr[0], arr[1], . . . , arr[arr.length-1] will be stored in sum.
(B) Sum of arr[1], arr[2], . . . , arr[arr.length-1] will be stored in sum.
(C) Sum of arr[0], arr[1], . . . , arr[arr.length] will be stored in sum.
(D) An infinite loop will occur.
(E) A run-time error will occur.

Answer 6

(E) A run-time error will occur.

Question 7

Consider this program segment:
for (int i = 2; i <= k; i++)
if (arr[i] < someValue)
System.out.print("SMALL");
What is the maximum number of times that SMALL can be printed?
(A) 0
(B) 1
(C) k - 1
(D) k - 2
(E) k

Answer 7

(C) k - 1

Question 8

6. What will be output from the following code segment, assuming it is in the same
class as the doSomething method?
int[] arr = {1, 2, 3, 4};
doSomething(arr);
System.out.print(arr[1] + " ");
System.out.print(arr[3]);
...
public void doSomething(int[] list)
{
int[] b = list;
for (int i = 0; i < b.length; i++)
b[i] = i;
}
(A) 0 0
(B) 2 4
(C) 1 3
(D) 0 2
(E) 0 3

Answer 8

(C) 1 3

Question 9

True or False?

Arrays are mutable.

Answer 9

True.

Arrays in Java are mutable; values at a specifc index can be changed. However, the size of an array cannot be altered.

Question 10

How would you declare and initialize a String array called “numbers” holding the values “one”, “two”, and “three”?

Answer 10

String[] numbers = {“one”, “two”, “three”};

OR

String[] numbers = new String[3];
numbers[0] = “one”;
numbers[1] = “two”;
numbers[2] = “three”;

Question 11

True or False? You can add objects of different types in an array.

Answer 11

False.

An array holds multiple values of the SAME type.

Question 12

public static void main(String[] args) {

int[] vec = {8,-2,4,5,-8};

foo(vec);

}

private static void foo(int[] x) {

for(int i = 0; i < x.length; i++) {

    int y = Math.abs(x[i]);

    for(int j = 0; j < y; j++) {

        System.out.print(x[i] + " ");

    }

    System.out.println();

}

}

Which of the following represents a possible output for the program above?

64

4

16

25

8 8 8 8 8 8 8 8

4 4 4 4

8 8 8 8 8 8 8 8

-2 -2

4 4 4 4

5 5 5 5 5

37
——————————————————-
64

-4

16

25

8 8 8 8 8 8 8 8

-2 -2

4 4 4 4

5 5 5 5 5

-8 -8 -8 -8 -8 -8 -8 -8

Answer 12

Correct answer:
8 8 8 8 8 8 8 8

-2 -2

4 4 4 4

5 5 5 5 5

-8 -8 -8 -8 -8 -8 -8 -8

Question 13

Which of the following is the correct method of accessing the 2nd value in an array:

i. value = array[2];
ii. value = array{2};
iii. value = array[1];

Answer 13

iii. indexing starts from 0, therefore the second object in the array will be at index 1. You will also specify the index in brackets.

Question 14

int[ ] x = {0, 1, 2, 3};
int temp;
int i = 0;
int j = x.length - 1;
while (i < j)
{
   temp = x[i];
   x[i] = x[j];
   x[j] = 2 * temp;
   i++;
   j--;
}

After the following code is executed which of the following are the values in x?

A. {3,2,2,0}
B. {0,1,2,3}
C. {3,2,1,0}
D. {0,2,4,6}
E. {6,4,2,0}

Answer 14

A. {3,2,2,0}

Question 15

Given the code segment: int[] arr = {1, 2, 3, 4, 5}; whic of the following would set the first two elements of array arr to 10, making the new value of array arr {10, 10, 3, 4, 5} ?
A. arr [0, 1] = 10
B. arr[1] = 10; arr [2] = 10;
C. arr = 10, 10, 3, 4, 5
D. arr[0] = 10; arr [1] = 10;

Answer 15

D. arr[0] = 10; arr [1] = 10;

Question 16

When arrays are declared, what are the elements initialized for automatically (default values)?
A. primitives: 1 boolean: true objects: null
B. primitives: 1 boolean: false objects: null
C. primitives: 0 boolean: false objects: null
D. primitives: 0 boolean: true objects: null

Answer 16

C. primitives: 0 boolean: false objects: null

Question 17

Is this the correct way of traversing an array? What is wrong with the for loop?

for(int i = 0; i < array.size; i++)
{
       // do stuff
}

Answer 17

No. You would use “.size()” to traverse an ArrayList, not an Array.
The correct method would be “array.length”.

Question 18

How do you determine the number of elements in an array?
int buses[] = new int[5];

A. buses.length

B. buses.length()

C. buses.size

D. buses.size()

Answer 18

A. buses.length

Question 19

int[] arrayOne = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

How do we access the even numbers in arrayOne from above?

Answer 19

2 = arrayOne[1]
4 = arrayOne[3]
6 = arrayOne[5]
8 = arrayOne[7]
10 = arrayOne[9]

Question 20

What import statement do you need to use before using an array?

Answer 20

import java.util.Arrays;